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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

3D Geolocation of Simulated Lightning Sources from Low-Earth Orbit

The recent removal of the Lightning Imaging Sensor from the International Space Station has left an observational gap in lightning detection from low-Earth orbit (LEO). However, new studies have demonstrated the potential for 3D geolocation of lightning sources using orbiting sensors. The Cubespark mission concept aims to take advantage of these developments by deploying a constellation of satellites with radio frequency (RF) sensors and optical imagers to not only map lightning locations, but also to collect bi-spectral flash images. These new capabilities include mapping storm charge structure, flash channel structure, and distinguishing microphysical processes throughout flash development, helping link microphysics and convective processes with overall flash and storm structure around the globe from LEO. In this study, we simulate lightning RF sources in the very high frequency (VHF) band, extrapolate their signals to space-based detection using an improved ionospheric model, and reconstruct their 3D locations using a time-of-arrival (TOA) minimization algorithm. Various constellation configurations, locations, and atmospheric conditions are considered in order to identify and quantify the three main sources of geolocation error: geometric, ionospheric, and instrumental effects. The promising results of this study emphasize the potential of space-based 3D lightning mapping under diverse conditions. 3D resolution is shown to be better than 1-2 km in many cases, enabling new global applications in meteorology and climate sciences. Here we present a selection of these geolocation results as seen from space alongside recent advancements, paving the way for a future generation of LEO lightning mappers.

CubeSpark↗
NASA NTRS2021

The NASA AfriSAR Campaign: Airborne SAR and Lidar Measurements of Tropical Forest Structure and Biomass in Support of Current and Future Space Missions

In 2015 and 2016, the AfriSAR campaign was carried out as a collaborative effort among international space and National Park agencies (ESA, NASA, ONERA, DLR, ANPN and AGEOS) in support of the upcoming ESA BIOMASS, NASA-ISRO Synthetic Aperture Radar (NISAR) and NASA Global Ecosystem Dynamics Initiative (GEDI) missions. The NASA contribution to the campaign was conducted in 2016 with the NASA LVIS (Land Vegetation and Ice Sensor) Lidar, the NASA L-band UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar). A central motivation for the AfriSAR deployment was the common AGBD estimation requirement for the three future spaceborne missions, the lack of sufficient airborne and ground calibration data covering the full range of ABGD in tropical forest systems, and the intercomparison and fusion of the technologies. During the campaign, over 7000 km2 of waveform Lidar data from LVIS and 30000 km2 of UAVSAR data were collected over 10 key sites and transects. In addition, field measurements of forest structure and biomass were collected in sixteen 1 hectare sized plots. The campaign produced gridded Lidar canopy structure products, gridded aboveground biomass and associated uncertainties, Lidar based vegetation canopy cover profile products, Polarimetric Interferometric SAR and Tomographic SAR products and field measurements. Our results showcase the types of data products and scientific results expected from the spaceborne Lidar and SAR missions; we also expect that the AfriSAR campaign data will facilitate further analysis and use of waveform Lidar and multiple baseline polarimetric SAR datasets for carbon cycle, biodiversity, water resources and more applications by the greater scientific community.

AfriSAR↗
NASA NTRS1995

A preliminary attempt to use neural networks for turbulent eddy classification

This note describes an attempt to use standard neural network tools to fashion a means of detecting eddy patterns in the wall region of a turbulent flow. The research was motivated by the desire to formulate a means to use only flow parameters that can be sensed on the wall to describe the passing eddy structure. If a simple formulation can be obtained, it could conceivably be utilized to control actuators embedded in the wall. Such actuators have been developed by Jacobson and Reynolds (1993a), Blackwelder and Liu (1994), Tung et al. (1995), and others. These actuators have the common characteristics that they are small and are typically flush with the wall when not deployed. When they are activated, it is assumed that they will be able to interact constructively with the turbulent eddies near their location to either decrease the wall shear stress, enhance or reduce the mixing, etc. At present, there is only a nascent understanding of the interaction dynamics between the actuators and the eddies in the flow. Nevertheless, for such interaction to succeed, methods to couple the actuators to the oncoming flow must be obtained. General methods must be found that will detect the space and temporal location of the desired structure. In particular, it will be necessary to know when the eddies will arrive at the location of the actuator. This research attempted to use the shear stress measurements on the wall in the vicinity of an actuator location to predict when a particular eddy pattern would arrive and/or occur at the designated location. In this work the eddy pattern to be detected was identified by its velocity signature only.

Blackwelder, Ron F.↗
NASA NTRS1981

Space assembly methodology

Large space structure assembly analysis techniques are defined and simulation activities are described. The simulations included are: an extravehicular activity assembly simulation; a fabricated beam assembly series using a beam generating machine end caps, and cross beam brackets; deployment of a deployable truss, using the neutral buoyancy remote manipulator system with crewman assistance; and a series aboard the KC-135 zero g aircraft.

Stokes, J. W.↗
NASA NTRS1981

Use of software tools in the development of real time software systems

The transformation of a preexisting software system into a larger and more versatile system with different mission requirements is discussed. The history of this transformation is used to illustrate the use of structured real time programming techniques and tools to produce maintainable and somewhat transportable systems. The predecessor system is a single ground diagnostic system; its purpose is to exercise a computer controlled hardware set prior to its deployment in its functional environment, as well as test the equipment set by supplying certain well known stimulas. The successor system (FTE) is required to perform certain testing and control functions while this hardware set is in its functional environment. Both systems must deal with heavy user input/output loads and a new I/O requirement is included in the design of the FTF system. Human factors are enhanced by adding an improved console interface and special function keyboard handler. The additional features require the inclusion of much new software to the original set from which FTF was developed. As a result, it is necessary to split the system into a duel programming configuration with high rates of interground communications. A generalized information routing mechanism is used to support this configuration.

Garvey, R. C.↗
NASA NTRSDate not supplied

A Rideshare Tensegrity Rover Concept to Explore Titan's Lands and Oceans

The Tension Adjustable Network for Deploying Entry Membrane (TANDEM) tensegrity robot is redesigned for a mission to Titan. Focus is on the design of the aeroshell and the use of tensegrity algorithm to optimize the configuration and loading of the tensegrity structure within the aeroshell.

N Deitrich↗
NASA NTRS1979

Study of wrap-rib antenna design

The results of a parametric design study conducted to develop the significant characteristics and technology limitations of space deployable antenna systems with aperture sizes ranging from 50 up to 300 m and F/D ratios between 0.5 and 3.0 are presented. Wrap/rib type reflectors of both the prime and offset fed geometry and associated feed support structures were considered. The significant constraints investigated as limitations on achievable aperture were inherent manufacturability, orbit dynamic and thermal stability, antenna weight, and antenna stowed volume. A data base, resulting in the defined maximum achievable aperture size as a function of diameter, frequency and estimated cost, was formed.

Wade, W. D.↗
NASA NTRS1993

Pointing and figure control system for a space-based far-IR segmented telescope

A pointing and figure control system for two space-based far-IR telescopes, the 10-20 m Large Deployable Reflector and the 3.6 m Submillimeter Intermediate Mission, is described. The figure maintenance control system is designed to counter the optical elements translational and rotational changes induced by long-term thermal drifts that the support structure may experience. The pointing system applies optical truss to telescope pointing; a laser metrology system is used to transfer pointing informaton from an external fine guidance sensor to the telescope optical boresight, defined by the primary mirror, secondary mirror, and focal plane assembly.

Lau, Kenneth↗
NASA NTRS2004

Autonomous NanoTechnology Swarm (ANTS) Prospecting Asteroid Mission (PAM), Asteroid Proximity Operations

The Autonomous NanoTechnology Swarm (ANTS) is a generic mission architecture based on spatially distributed spacecraft, autonomous and redundant components, and hierarchical organization. The ANTS Prospecting Asteroid Mission (PAM) is an ANTS application which will nominally use a swarm of 1000 spacecraft. There would be 10 types of "specialists" with common spacecraft buses. There would be 10 subswarms of approximately 100 spacecraft each or approximately 10 of each specialist in each swarm. The ANTS PAM primary objective is the exploration of the asteroid belt in search of resources and material with astrobiologically relevant origins and signatures. The ANTS PAM spacecraft will nominally be released from a station in an Earth-Moon L1 libration point orbit, and they will use Solar sails for propulsion. The sail structure would be highly flexible, capable of changing morphology to change cross-section for capture of sunlight or to form effective "tip vanes" for attitude control. ANTS PAM sails would be capable of full to partial deployment, to change effective sail area and center of pressure, and thus allow attitude control. Results of analysis of a transfer trajectory from Earth to a sample target asteroid will be presented. ANTS PAM will require continuous coverage of different asteroid locations as close as one to two asteroid "diameters" from the surface of the asteroid for periods of science data collection during asteroid proximity operations. Hovering spacecraft could meet the science data collection objectives. The results of hovering analysis will be presented. There are locations for which hovering is not possible, for example on the illuminated side of the asteroid. For cases where hovering is not possible, the results of utilizing asteroid formations to orbit the asteroid and achieve the desired asteroid viewing will be presented for sample asteroids. The ability of ANTS PAM to reduce the area of the solar sail during asteroid proximity operations is critical to the maintenance of orbiting formations for a period of time. Results of analysis of potential "traffic" problems during asteroid proximity operations will be presented.

Marr, Greg↗
NASA NTRS2004

A Survey of Collectives

Due to the increasing sophistication and miniaturization of computational components, complex, distributed systems of interacting agents are becoming ubiquitous. Such systems, where each agent aims to optimize its own performance, but where there is a well-defined set of system-level performance criteria, are called collectives. The fundamental problem in analyzing/designing such systems is in determining how the combined actions of self-interested agents leads to 'coordinated' behavior on a iarge scale. Examples of artificial systems which exhibit such behavior include packet routing across a data network, control of an array of communication satellites, coordination of multiple deployables, and dynamic job scheduling across a distributed computer grid. Examples of natural systems include ecosystems, economies, and the organelles within a living cell. No current scientific discipline provides a thorough understanding of the relation between the structure of collectives and how well they meet their overall performance criteria. Although still very young, research on collectives has resulted in successes both in understanding and designing such systems. It is eqected that as it matures and draws upon other disciplines related to collectives, this field will greatly expand the range of computationally addressable tasks. Moreover, in addition to drawing on them, such a fully developed field of collective intelligence may provide insight into already established scientific fields, such as mechanism design, economics, game theory, and population biology. This chapter provides a survey to the emerging science of collectives.

Tumer, Kagan↗
NASA NTRS2004

Controllable Curved Mirrors Made from Single-Layer EAP Films

A document proposes that lightweight, deployable, large-aperture, controllable curved mirrors made of reflectively coated thin electroactive-polymer (EAP) films be developed for use in spaceborne microwave and optical systems. In these mirrors, the EAP films would serve as both structures and actuators. EAPs that are potentially suitable for such use include piezoelectric, electrostrictive, ferroelectric, and dielectric polymers. These materials exhibit strains proportional to the squares of applied electric fields. Utilizing this phenomenon, a curved mirror according to the proposal could be made from a flat film, upon which a nonuniform electrostatic potential (decreasing from the center toward the edge) would be imposed to obtain a required curvature. The effect would be analogous to that of an old-fashioned metalworking practice in which a flat metal sheet is made into a bowl by hammering it repeatedly, the frequency of hammer blows decreasing with distance from the center. In operation, the nonuniform electrostatic potential could be imposed by use of an electron gun. Calculations have shown that by use of a single- layer film made of a currently available EAP, it would be possible to control the focal length of a 2-m-diameter mirror from infinity to 1.25 m.

Bao, Xiaoqi↗
NASA NTRS2011

Flexible Ablators: Applications and Arcjet Testing

Flexible ablators were conceived in 2009 to meet the technology pull for large, human Mars Exploration Class, 23 m diameter hypersonic inflatable aerodynamic decelerators. As described elsewhere, they have been recently undergoing initial technical readiness (TRL) advancement by NASA. The performance limits of flexible ablators in terms of maximum heat rates, pressure and shear remain to be defined. Further, it is hoped that this emerging technology will vastly expand the capability of future NASA missions involving atmospheric entry systems. This paper considers four topics of relevance to flexible ablators: (1) Their potential applications to near/far term human and robotic missions (2) Brief consideration of the balance between heat shield diameter, flexible ablator performance limits, entry vehicle controllability and aft-body shear layer impingement of interest to designers of very large entry vehicles, (3) The approach for developing bonding processes of flexible ablators for use on rigid entry bodies and (4) Design of large arcjet test articles that will enable the testing of flexible ablators in flight-like, combined environments (heat flux, pressure, shear and structural tensile loading). Based on a review of thermal protection system performance requirements for future entry vehicles, it is concluded that flexible ablators have broad applications to conventional, rigid entry body systems and are enabling to large deployable (both inflatable and mechanical) heat shields. Because of the game-changing nature of flexible ablators, it appears that NASA's Office of the Chief Technologist (OCT) will fund a focused, 3-year TRL advancement of the new materials capable of performance in heat fluxes in the range of 200-600 W/sq. cm. This support will enable the manufacture and use of the large-scale arcjet test designs that will be a key element of this OCT funded activity.

Thermal Protection↗
NASA NTRS2020

A Review of Welding in Space and Related Technologies

Deployment of welding and additive manufacturing (AM) technologies in the space environment has the potential to revolutionize how orbiting platforms are designed, manufactured, and assembled. These technologies offer the option for repair of sustained damage to habitat structures on space missions, as astronauts would be able to manufacture new parts (using welding-derived AM processes suitable for use in the external space environment) and weld cracks. An added benefit is that required repairs can be achieved more economically, as new parts need not be shipped from Earth. With further maturation of in-space welding capabilities, astronauts could operate under given standards and weld damaged structures rather than rely on cargo resupply. This Technical Memorandum (TM) begins by reviewing the available literature relevant to welding in space, focusing on solidification, heat and mass transfer, and fluid flows in microgravity. This survey considers research on the effects of welding in microgravity on a material system. The various in-space welding devices that have been previously designed and tested are examined to determine their capabilities and shortcomings, with a focus on the results of their individual welding experiments. Safety measures are discussed to protect the orbiting International Space Station (ISS) and crew during welding operations. Finally, the state of the art is examined by focusing on current approaches to AM and on-orbit welding that are being developed by several companies in conjunction with NASA.

Naden, N.↗
NASA NTRS1983

Requirements for a mobile communications satellite system. Volume 3: Large space structures measurements study

This study report defines a set of tests and measurements required to characterize the performance of a Large Space System (LSS), and to scale this data to other LSS satellites. Requirements from the Mobile Communication Satellite (MSAT) configurations derived in the parent study were used. MSAT utilizes a large, mesh deployable antenna, and encompasses a significant range of LSS technology issues in the areas of structural/dynamics, control, and performance predictability. In this study, performance requirements were developed for the antenna. Special emphasis was placed on antenna surface accuracy, and pointing stability. Instrumentation and measurement systems, applicable to LSS, were selected from existing or on-going technology developments. Laser ranging and angulation systems, presently in breadboard status, form the backbone of the measurements. Following this, a set of ground, STS, and GEO-operational were investigated. A third scale (15 meter) antenna system as selected for ground characterization followed by STS flight technology development. This selection ensures analytical scaling from ground-to-orbit, and size scaling. Other benefits are cost and ability to perform reasonable ground tests. Detail costing of the various tests and measurement systems were derived and are included in the report.

Akle, W.↗
NASA NTRS2009

Modeling and Testing of Phase Transition-Based Deployable Systems for Small Body Sample Capture

This paper summarizes the modeling, simulation, and testing work related to the development of technology to investigate the potential that shape memory actuation has to provide mechanically simple and affordable solutions for delivering assets to a surface and for sample capture and return. We investigate the structural dynamics and controllability aspects of an adaptive beam carrying an end-effector which, by changing equilibrium phases is able to actively decouple the end-effector dynamics from the spacecraft dynamics during the surface contact phase. Asset delivery and sample capture and return are at the heart of several emerging potential missions to small bodies, such as asteroids and comets, and to the surface of large bodies, such as Titan.

flexible appendage↗
NASA NTRS1993

The MESUR Mission

The MESUR mission will place a network of small, robust landers on the Martian surface, making a coordinated set of observations for at least one Martian year. MESUR presents some major challenges for development of instruments, instrument deployment systems, and on board data processing techniques. The instrument payload has not yet been selected, but the straw man payload is (1) a three-axis seismometer; (2) a meteorology package that senses pressure, temperature, wind speed and direction, humidity, and sky brightness; (3) an alphaproton-X-ray spectrometer (APXS); (4) a thermal analysis/evolved gas analysis (TA/EGA) instrument; (5) a descent imager, (6) a panoramic surface imager; (7) an atmospheric structure instrument (ASI) that senses pressure, temperature, and acceleration during descent to the surface; and (8) radio science. Because of the large number of landers to be sent (about 16), all these instruments must be very lightweight. All but the descent imager and the ASI must survive landing loads that may approach 100 g. The meteorology package, seismometer, and surface imager must be able to survive on the surface for at least one Martian year. The seismometer requires deployment off the lander body. The panoramic imager and some components of the meteorology package require deployment above the lander body. The APXS must be placed directly against one or more rocks near the lander, prompting consideration of a micro rover for deployment of this instrument. The TA/EGA requires a system to acquire, contain, and heat a soil sample. Both the imagers and, especially, the seismometer will be capable of producing large volumes of data, and will require use of sophisticated data compression techniques.

Squyres, S. W.↗
NASA NTRS2019

Modeling, Simulation, and Robust Design of the TSIS Pointing Controller for ISS Deployment

To ensure high quality TSIS science measurements, stringent requirements were levied on the pointing system performance. Several factors complicated the design of the pointing system controller including uncertainty in knowledge of the ISS base motion jitter, the use of direct drive brushless DC motors for the gimbal system, and the presence of TSIS structure low frequency modes. This paper will describe the modeling, simulation, analysis, and robust design techniques employed to reduce risk resulting in a pointing system that met requirements on-orbit.

Engelmann, Andrew↗